1. Technical Field
This disclosure relates to a belt accessory drive for a motor vehicle and in particular to a method of reducing variations in drive belt tension produced by fluctuations in engine speed.
2. Background Art
It is well known to use an accessory drive system on a motor vehicle that requires a belt to transmit drive from a driving pulley attached to the output from an engine to a driven pulley used to drive the accessory. One example of such an accessory drive system is a crank damper of an internal combustion engine driving an electrical generator such as an alternator.
In a normal alternator drive system the electrical load on the belt from the alternator is relatively constant and the belt drive system accelerates and then decelerates the alternator cyclically in phase with engine speed fluctuations due to the combustion process occurring within the engine. This acceleration and deceleration of the belt drive system results in variations in the tension in the belt which if not allowed for in the design of the belt drive system can result in extremes of tension. Excessively high tension can cause premature belt aging leading to early failure or bearing failure either in the engine, the alternator or other accessories driven by the same belt. Excessively low tension can result in belt slippage with resultant high belt wear and noise.